x86_64 only:
	* gendef (_sigfe_maybe): Drop pushing %r12, use %r10 instead since we
	don't call yield anymore.
	(_sigfe): Ditto.
	(_sigbe): Ditto.
Fix internal error caused by interaction between catch signal and fork
	* fhandler.h (class fhandler_dev_random): Change type of pseudo to
	uint32_t to make sure it's 32 bit on all supported platforms.
	* globals.cc (__isthreaded): New global variable.  Explain what it's
	used for.
	* miscfuncs.cc (thread_wrapper): Set __isthreaded to 1 here.